1. Field of the Invention
This invention relates to a dart-type airship with high propulsive efficiency.
2. Description of the Prior Art
The realization of an airship with high propulsive efficiency can be expected to make possible the development of high-altitude stationary platforms and airships driven by solar energy and thus to contribute to the solution of the world's environmental problems. It can also be expected to advance today's information-intensive society by expanding the capabilities of radio relay systems and remote sensing systems.
In one airship hull design for realizing high-efficiency propulsion, air flowing along the hull surface is sucked in through ducts and then blown aft as a jet. This system, known as the boundary layer control propulsion system, prevents flow separation and restores pressure at the tail, thus achieving a reduction in overall resistance. Fluid dynamic studies on the boundary layer control propulsion system conducted by Fabio R. Goldschmied of the U.S. using an airship with a dart-type tail structure consisting of a tail boom and an empennage at the aft end of the boom confirmed an increase in propulsive efficiency in wind tunnel tests. Nonetheless, the system was not adopted by the U.S. Navy's HASPA Project because it was found to be structurally impossible to realize.
In an airship with a dart-type tail structure, the propulsion fan for the suction and jetting of air and the motor for driving the fan have to be installed in the tail section. Moreover, the empennage has to be positioned even further aft via a boom. Since this makes the aft of the hull extremely heavy, it becomes difficult to realize a viable airship structure.